Oversize return for mills



Apr. 3, 1923,

1,450,290 H. w. HARDINGE I OVERSIZE RETURN FOR MILLS;

Filed. June 4, 1920 A TTORNEYJ.

Patented Apr. 3, 1923.

HARRY W.- HARDINGE, NEW YORK, N. Y.

OVERSIZE RETURNFOR MILLS.

Application filed June 4, 1920. Serial No, 386,527.

To all whom it may concern:

Be it known that I, HARRY W. HARDINGE, a citizen of the United States ofAmerica, residing at New York, in the county and State of New York, haveinvented certain new and useful Improvements in Oversize Returns forMills, of which the following is a full, clear, and exact description.

The invention which constitutes the. subject matter of this applicationrelates to grinding mills and has for one of its principal objects toprovide a novel form of means for automatically returning oversizematerial which is discharged from suchmills to the rotating drum thereoffor regrinding. In the operation of cylindrical grinding mills a certainamount of oversize material is discharged along with the fines. Inconical mills the percentage of oversize discharged is comparativelysmall due to the inherent classifying action of this type of mill.'Nevertheless in the latter type of mills, crowded or operated beyondnormal .capacity, there is a certain amount of over- 5 size inthedischarge. In accordance with the present invention I provide aclassifier of cylindrical,-conical or. other suitable form, into whichthe drum discharges, and provide means for automatically returningoversize material from the classifier to the grinding drum through theoutlet opening of the latter, for regrinding. Numerous advantages whichare incidentto this arrangement will be apparent as some of the phys- 7'ioal embodiments are hereinafter described.-

Referring to the drawings which illustrate what I now consider preferredforms of my invention: j

Fig. 1 is a somewhat diagrammatic sectional elevation of a conical millembodying my invention.

Fig. 2 is a section on the line 2-2 of Fig. 1.

Directing attention to Fig. 1 it will be seen that the mill there showncomprises adrum 1 journaled for. rotation in bearings 2, 2. The saiddrum is adapted to receive material to be ground through the inlettrunnion 4,to grmd o'r disintegrate the same, to classify it accordingto size by means of the .conical outlet 3, and to discharge the finesthrough the outlet trunnion 5, It will be understood, of course, thatthe drum '1 may be rotated by ,any suitable means and provided withballs, pebbles, rods or other suitable grinding media well known in theart.

As stated above a certain amount of overslze is discharged with thefines through the outlet opening 5. I therefore provide a classifier toreceive the discharge of the drum 1 and automaticall to separate theoversize from the fines. ne form of classifier is shown in Figs. 1 and 2and comprises a substantially cone-shaped barrel 6 secured at its baseto the outlet trunnion of the drum 1 to rotate therewith. It will. benotedthat thebarrel 6 is provided with an opening 7, which registerswith the outlet opening 5, and an outlet opening 8." Water or otherliquid is supplied to the barrel 6 in'any one or more of various ways.If the drum 1 is to perform wet grinding, water may be supplied with theprimary mate'rial through the inlet opening 4, or in a mannerhereinafter more specifically described. The water so introduced willthen flow through the drum 1 and out through the opening 5 into thebarrel 6. The outlet opening 5 is'preferably so arranged that its bottomo'r lower part is lower than the bottom of the inlet opening 4. Thewater entering the barrel 6 at 7 flows therethrough and leaves atopening 8, the lower edge of which is preferably lower than the lower'edge of openings 5 and 7. The

fines leaving the drum 1 and entering the barrel 6 flow through. thelatter with the stream. of water and are discharged at 8, but theoversize material, being heavier, sinks to the bottom of the barrel 6.If desirable water or liquid may be supplied to the barrel 6 through astationary pipe or conduit 9.

Means are also provided for automatically returning the oversize fromthe barrel 6 to the druml for regrindi-n One form of such means isillustrated in Figs. 1 and 2 and may be constructed substantially asfollows. A conveyer or conduit 10 extends, from the barrel 6,substantially axially into thedrum 1 through the opening 5 of thelatter. The conveyor 10 terminates, inside the barrel 6, in one or morebranches 11, each communicating at one end with the pipe 10 and eachadapted at its other end to scoop up oversize from the bottom of thebarrel 6 when thebranches 11 are rotated in the direction of the arrowshown, in Fig. 2. In order to cause rotation of the conveyer 10-11 thebranches 11,11 may be secured to the base of the cone-shaped barrel 6 bymeans of cleats or straps 12 clearly shown in Fig. 2. Obviously onrotation of the barrel 6 in thedirection of the arrow (Fig. 2) theoversize will be scooped up from the bottom of the barrel 6 and impelledthrough the tube 10 into the drum 1, there to be subjected toregrinding. If it is desired to increase the fiow of the oversizethrough theconveyer 11-1U, the latter may be provided with anaxialopening 13 through which a suitably supported stationary nozzle 14extends, said nozzle being supplied with liquid or gas under pressure. i

The operation of the mill shown in Figs. 1 and 2 will be clear to thoseskilled in the art,.in view of the foregoing description.

Among other advantages, I Wish to call attention to the fact that myinvention may readily be.applied to mills which are already built or inuse. The oversize-return conveyer lies within the lateral confines ofthe grinding drum thus minimizing space and protecting the saidconveyer. Also, in view of the function performed, the length of theconveyer tubes or pipes is minimized.

In accordance with the provisions of the patent statutes, I have hereindescribed the principal of operation of my invention, together with theapparatus which I now consider to represent the best embodiments.

thereof but I desire to have it understood that the apparatus shown isonly illustrative and that the invention can be carried out by othermeans. signed to use the various features and elements in thecombination and relations described, some' of these may be altered andothers omitted without interfering with the more general results andeffects outlined, and

the invention extends to such use.

What I claim is: i

1. A grinding-mill comprising in combination, a rotatable grinding drumhaving a substantially unobstructed overflow conical outlet portion forthe classification of material according to size, a classifier intowhich said drum discharges, and means for automatically returningoversize material from said classifier to said drum through the end ofsaid conical outlet portion.

2. In combination, a rotatable grinding drum having a substantiallyunobstructed overflow conical outlet portion for the classification ofmaterial according to size, a substantially cone-shaped rotatableclassifying member into which said drum discharges, and meansfor'returning oversize material from said classifier to said drumthrough .the end of said conical outlet portion while said drum andmember are rotatingf 3. In combination, a rotatable grinding drum havinga substantially unobstructed Also, while it is deoverflow conical outletportion for the classification of material according to size, asubstantially cone-shaped classifier secured to said drum to rotatetherewith and to receive the discharge therefrom, and a conveyer tuberotatable with said drum, extending at one end into the conical outletthereof and terminating at its opposite end in at least one armcommunicating with said classifier adjacent the large portion of thelatter.

4. A grinding mill comprising in combination, a rotatable grinding drumhaving a substantially unobstructed overflow conical outlet portion forthe classification of material according to size, a second drum intowhich said first named drum discharges, and means comprising a spiralconveyer for returning oversize material from said second drum to saidfirst drum through the end of the conical outlet of the latter, saidsecond drum having a sloping wall for deflecting material toward aninlet end of said spiral conveyer.

5. A grinding mill comprising in combination, a rotatable grinding drumhaving a substantially unobstructed overflow conical outlet portion forthe classification of material according to size, a classifier intowhich said drum discharges, and means for automatically returningoversize material from said classifier through said conical out- 7 letportion to the interior of said drum at a point nearer to the base ofthe conical outlet than to the apex thereof.

6. In combination, a rotatable grinding drum having a substantiallyunobstructed overflow conical outlet portion for the classification ofmaterial accordingto size,

a classifier into which said drum discharges, means for causing liquidto flow through said classifier to carryout the fines, and means forautomatically returning oversize material from said classifier to saiddrum through said conical outlet portion.

7. In combination, a rotatable grinding drum having a substantiallyunobstructed overflow conical outlet portion for the classification ofmaterial according to size, a substantially cone-shaped classifiersecured at its larger end to said drum to rotate with said drum and toreceive the discharge therefrom. and a conveyer tube rotatablewith saiddrum, extending at one end into the conical outlet thereof and havinganother end in communication with said classifier adjacent the largerend of the latter.

8 In combination, a rotatable grinding drum having a trunnion outletportion, a classifier secured to said drum to rotate therewith and toreceive the discharge therefrom, a conveyer tube rotatable with saiddrum, having an end extending into said trunnion outlet and another endin communication with said classifier, and means for supplying fluidunder pressure to 'said tube to impel material therethrough.

troduction of material'to be disintegrated;

a conical outlet and means connecting the same at its base to the lnletportion, the slant of the lower side of the said conical outlet portionrelative to the perpendicular or direction of gravity being not lessthan 45 nor more than 70, approximately, means for supporting the barrelfor rotation about its longitudinal axis, a classifier into which saiddrum discharges, and means for automatically returning oversize materialfrom said classifier to said barrel through the end of said conicaloutlet while said barrel is rotating.

In testimony whereof I hereto afiix my signature.

HARRY W. HARDINGE.

